I just purchased a new set of NAD components, the T163 and T973 but now have what I beleive to be a ground loop problem. I have read much about the issue, though I feel that perhaps I may have something a bit more complex.

The problem exists even when I have nothing connected to the pre except the amp and speakers. The noise is evident from the front towers in stereo mode, and in multichannel selection it gets extremely loud in all channels. The sub adds to the problem (EP500) when it is connected, though it is not the only source of the issue.

What I do not understand is that the noise does not exist when just the amp is plugged into power and connected to the speakers, however when the pre is attached and powered on the noise is evident. So this means it has something to do with the pre & amp, though the pre is a two prong and the amp is three. All of the components are connected to the same power source, and line conditioners have not worked. I can get the buzz to lower by lowering the gains on the back of the amp, though this effects sound quality and level.

My old sony receiver had none of these problems and it was attached in the same maner.

Please if anyone has any ideas I would appreciate them.

(I posted a similar thread on AVS forums and have had some very nice people attempt to help me)